A shark that swam from New Zealand to Fiji has returned home for Christmas, rounding off an 11,000km odyssey and amazing the scientists who tracked her journey.

In May, "Carol" became the first mako shark in New Zealand waters to be tracked with a satellite "spot" tag, under a Niwa research project funded by the Ministry for Primary Industries and Nova-Southeastern University in Florida.

Scientists watched in amazement as she set off for the Pacific Islands, only to change her mind halfway and turn back for a two-month stay near Ninety Mile Beach.

After a loop around the top of the North Island, the shark again set off for Fiji, reaching her destination in September.

It was what she did next - returning to New Zealand and arriving home only 100km from the spot where she was tagged - that most surprised scientists.

In the space of seven months, the 1.8m shark clocked up more than 11,300km, covering up to 100km a day.

This month, she cruised around the East Cape and was tracked near Mahia a few days ago, probably bound for Napier.